Apparatus for damping vibrations in stock suspension flow

Abstract

Fibrous stock suspension preparation systems include moving parts that generate a vibration impulse flow in the outlet from the preparation system. A counter-vibration impulse generator is connected to the outlet pipe and includes a correcting impulse recorder also connected to the outlet pipe for sensing the vibrations of the flow therepast and for sending a signal to the counter-vibration generator to control the amplitude and/or the frequency of the counter-vibration generator. A further impulse recorder between the stock suspension preparation system and the first mentioned impulse recorder is also connected to the outlet pipe for providing a stock transit time correction signal for correcting the signal of the first mentioned impulse recorder.

What is claimed is: 
     
       1. Control apparatus for damping the vibration in a preparation system for preparing stock suspensions, the preparation system including means which produce stock suspension and in the process generate vibration impulses in the stock suspension, the preparation system including an outlet conduit for prepared stock suspension, the outlet conduit being conducted with the preparation system for carrying a flow of stock suspension in which vibration impulses have been generated;   the control apparatus comprising:   first sensing means for sensing the vibration impulses in the flow of stock suspension in the outlet conduit;   means connected into the outlet conduit for producing counter-vibrations in the flow of stock suspension and for generating vibrations which are out of phase with the vibration impulses that are generated in the flow of stock suspension for damping the vibrations in the flow of stock suspension;   the first sensing means being connected with the means for producing counter-vibrations for adjusting at least one of the frequency and amplitude of the counter-vibrations produced by the means for producing counter-vibrations for maintaining the out of phase relationship and for maintaining a sufficiently elevated level of counter-vibrations at a frequency and an amplitude selected to damp the vibration impulses in the flow of stock suspension;   an impulse recorder connected into the outlet conduit downstream of the preparation system and of the first sensing means for generating a transit time correction signal for the transit of vibrations through the stock suspension for controlling the first sensing means.   
     
     
       2. The apparatus of claim 1, wherein the means for producing counter-vibrations comprises a magnetizable metal core in an electric coil, the coil being connected with the means for sensing vibration impulses in the stock flow, whereby an electric signal corresponding to the stock flow vibrations communicates to the coil. 
     
     
       3. Control apparatus for damping the vibration in a preparation system for preparing stock suspensions, the preparation system including means which produce stock suspension and in the process generate vibration impulses in the stock suspension, the preparation system including an outlet conduit for prepared stock suspension, the outlet conduit being connected with the preparation system for carrying a flow of stock suspension in which vibration impulses have been generated;   the control apparatus comprising:   first means for sensing the vibration impulses in the flow of stock suspension in the outlet conduit;   means connected into the outlet conduit for producing counter-vibrations in the flow of stock suspension and for generating vibrations which are out of phase with the vibration impulses that are generated in the flow of stock suspension for damping the vibrations in the flow of stock suspension;   the first sensing means being connected with the means for producing counter-vibrations for adjusting at least one of the frequency and amplitude of the counter-vibrations produced by the means for producing counter-vibrations for maintaining the out of phase relationship and for maintaining a sufficiently elevated level of counter-vibrations at a frequency and an amplitude selected to damp the vibration impulses in the flow of stock suspension;   a second means for sensing vibration impulses in the flow of stock suspension in the outlet conduit comprising a correcting impulse recorder connected into the outlet conduit downstream in the direction of the flow of stock suspension from the connection to the outlet conduit of the means for producing counter-vibrations, the second means for measuring the amplitude of the counter-vibrations in the flow of stock suspension in the outlet conduit, and the second means being connected to the means for producing counter-vibrations in a manner for providing a signal for adjusting the amplitude of the counter-vibrations.   
     
     
       4. The apparatus of claim 3, further comprising a second impulse recorder connected into the outlet conduit downstream of the preparation system and the first mentioned impulse recorder for generating a transit time correction signal for the transit of vibrations through the stock suspension for controlling the first impulse recorder. 
     
     
       5. The apparatus of claim 3, further comprising means for connecting the output of the second means as a feedback signal into the first means. 
     
     
       6. The apparatus of claim 3, wherein the means for producing the counter-vibrations comprises a magnetizable metal core in an electric coil, the coil being connected with the means for sensing vibration impulses in the stock flow, whereby an electric signal corresponding to the stock flow vibrations communicates to the coil.